Sydney - A new record time for Australia's toughest yacht race could be thwarted by shifting winds in the notoriously wild Bass Strait after the 2018 Sydney-Hobart begins on Wednesday.
The forecast is for a gusty start with a favourable strong north-easterly breeze, although a possible southerly change could thwart the supermaxis' record bid and turn the treacherous strait into "a parking lot".
The gruelling annual contest, in its 74th edition, will see 85 yachts depart Sydney Harbour on Boxing Day, December 26, 04:00 for the brutal 1 163-kilometre dash across the Tasman Sea to Hobart.
This year's bluewater classic will mark the 20th anniversary of a fatal storm that saw six sailors lose their lives in mountainous seas and wild winds as strong as those in a category two tropical cyclone.
The devastating deep depression that struck in 1998 saw just 44 yachts out of 115 finish the race, with sailors this year set to observe a moment of silence on Thursday.
The Bureau of Meteorology said Boxing Day morning would feature light winds, before a "very stiff north to northeasterly sea breeze" develops in the afternoon.
"If it is a fairly early sea breeze, we could see quite a fast start for the yachts... going out of (Sydney) Heads," the bureau's senior meteorologist Simon Louis told AFP.
Predictions had been for north to north-easterly winds of up to 25 knots with gusts to 35 knots along the entire route.
But latest forecasts indicate a possibility of a trough developing over the eastern Bass Strait between Tasmania and the Australian mainland.
"If that happens, then we'll see much lighter winds developing in the second half of the race over eastern Bass Strait and eastern Tasmania."
Such a situation could turn the Bass Strait into a "parking lot", quipped David Sudano, the navigator for 51-footer Primitive Cool.
Also standing between the yachts and a new race record is Hobart's famously sluggish River Derwent, which could slow the front runners by hours with its windless holes.
Described as the "Everest" of ocean racing, this year's Sydney to Hobart features five supermaxis - including last year's record-breaking Comanche - and 13 international entrants.
The 100-footer Comanche set a new record of one day, nine hours, 15 minutes and 24 seconds in 2017 and was named the line honours winner after rival supermaxi Wild Oats XI was stripped of the title over a near-collision.
Wild Oats XI had crossed the line in record time, but was handed a one-hour penalty by an international jury after the incident.
Other supermaxis in contention are Black Jack, InfoTrack and Hong Kong's Scallywag.
"This is the toughest fleet I've seen in the history of the event," said Mark Richards, skipper of eight-time line honours winner Wild Oats.
Owner-skipper Matt Allen of last year's Tattersall Cup overall handicap winner, Ichi Ban, is aiming to be the first person to claim back-to-back victories in over 50 years.
The handicap honours go to the vessel that performs best according to size, and Allen's TP52 is again among the favourites.
"We know a lot more about the boat than we did this time last year and we are more confident in the boat, our sails and rig set-up," he said.
"All the crew are looking forward to the challenge of going back-to-back - and the forecast is looking pretty good for 50 footers."